over 3 years ago - Hackaloken - Direct link
The error message shown in red (Failed to log in. if this problem persists please contact support) is the main problem here, and can be caused by a few things.
We changed login from using Usernames to using email addresses in patch 0.7.3, so we added that message in case people were unaware. Please make sure you’re using the email address for your account, rather than username.
Are you on Steam or the Standalone client? Have you been able to login successfully in the past? Your log file and system information would be helpful as well if the issue persists.